Exposure to toxic levels of transition metals, or a lack of the essential zinc, represents worldwide health problems that affect reproductive success. Metallothioneins (MT) are a unique, multi-functional group of metal-binding proteins that help protect the developing mammalian conceptus from these insults. MT expression is specifically up-regulated in the visceral endoderm and the maternal deciduum, which surround the embryo during development. Our long-term objective is to elucidate the mechanisms that regulate MT expression in the visceral yolk sac and maternal decidual cells. The specific aims of the proposed research are 1) to identify proteins that interact with MT-I and/or E-box1 to regulate mouse MT-I expression in the visceral yolk sac; proteins that interact with MTF-I and/or E-box1 to regulate mouse MT-I expression to the visceral yolk sac;' and 2) to identify transcription factors which bind the proximal MT-I promoter (-540-bp to -20-bp) and 2) to identify transcription factors which bind the proximal MT-I promoter (-540-bp to -250-bp) and regulate cell-specific gene expression in the maternal deciduum. These aims will be accomplished using transgenic, yeast- hybrid screening, and traditional biochemical approaches. The proposed research will identify additional cis- and trans-acting factors involved in regulating MT-I expression, and will make a significant contribution to our understanding of gene-regulatory mechanisms that serve protective functions during pregnancy.